Headstock for lathes and the like



Oct. 27, 1959 T. V. WILLIAMS HEADSTOCK FOR LATHES AND THE LIKE FiledApril 19, 1957 T Memr Unite rmAnsrocK non LATHES AND THE Lnm ApplicationApril 19, 1957, Serial No. 653,835

2 Claims. (CI. 82-40) This invention relates to headstocks of the typehaving a conical center for engagement in a central recess in the end ofthe stock and driving dogs engaging the end of the stock in spacedrelation to the center for turning the stock.

Objects of the invention are to provide a headstock which is simple andeconomical in construction, in which the dogs automatically bite intothe end of the stock in response to pressure from the tailstock, inwhich the dogs automatically adjust to irregularity in the stock so thateach dog gets a firm grip on the stock, and which is durable andreliable in use.

According to the present invention the headstock has an axial bore forthe center and one or more off-center bores for the driving dog or dogs,the center and dogs being slidable endwise in the bores, together withhydraulic or other means for forcing the dogs outwardly when the centeris forced inwardly. In the preferred embodiment the head has an interiorpassageway interconnecting the rear ends of the bores, the passagewayand the aforesaid ends being filled with grease or other fluid so thatthe dogs are forced outwardly when the center is forced inwardly. Whenusing a plurality of driving dogs they are preferably distributedequidistantly around the center bore.

For the purpose of illustration a typical embodiment of the invention isshown in the accompanying drawings in which:

Fig. 1 is an end View;

Fig. 2 is a side view with parts broken away;

Fig. 3 is a section on line 3-3 of Fig. 1; and

Fig. 4 is a section on line 4-4 of Fig. 2.

The particular embodiment of the invention chosen for the purpose ofillustration comprises a headstock formed in two parts 1 and 2, thefront part 2 fitting in a recess in the forward face of the rear part 1and the two parts being secured together by means of screws 3. The rearpart 1 may be mounted on the face of the rotating part of a lathe 4 bymeans of screws extending through the openings 6. The forward part 2 isprovided with an axial bore 7 and three smaller bores 8 radially offsetfrom the axial bore and uniformly distributed around the axial bore.Slidably fitted in the axial bore is a center 9, the rear end of thebore being enlarged and the center having a flange 10 seating againstthe shoulder between the two bores. The center 9 is urged forwardly bymeans of a spring 11. Slidably mounted in each of the offset bores is aplunger 12 having on its rearward end a flange 13 fitting in theenlarged rearward portion of the bore 8. A spring 14 between the flange13 and the shoulder between the two bores urges the plunger 12rearwardly. The forward end of each of the plungers 12 is bifurcatedradially and in the bifurcation is pivotally mounted a dog 16 on a pin17, the forward edges of the dogs being beveled circumferentially sothat the leading edges bite into the end of the stock S. The inner endof each dog preferably extends into a recess 18 in the center 9. Whilethe inner ends of the dogs should fit the recesses fairly snugly, theyshould be freely movable in the recesses so that the dogs areself-aligning. The rear Patent M 2,909,955 Patented Oct. 27, 1959 endsof the bores interconnect through a passageway 19 in the part 1. Asshown by stippling the rear ends of the bores and the passageway 19 arefilled with a fluid such as grease, so that when the center 9 is forcedrearwardly the plungers 12 are forced forwardly. The passageway 19 maybe filled through a fitting 21 and duct 22 with a bleeder 23 in theopposite end of the duct which is removed during the filling operation.Around the center 9 and the plungers 12 are provided sealing irlingis 24and 26 to prevent the escape of the aforesaid In the absence of stockthe center 9 is held in its forward position by spring 11 and theplungers 12 are held in their rearward positions by springs 14 so thatthe center 9 projects beyond the dogs 16 as shown in Fig. 2. When thestock S is placed between the headstock and tailstock in the usual way,adjustment of the tailstock toward the headstock forces the center 9 tothe rear against the action of spring 11 and this movement of the centerforces the plunger 12 forwardly to embed the dogs 16 in the end of thestock. Owing to the fact that each plunger moves independently of theothers under the same pressure, the dogs 16 embed themselves in the endof the stock uniformly, notwithstanding irregularities in the shape ofthe stock. When the stock is removed the springs return the parts to theposition shown in Fig. 2. As illustrated the area of the rear end ofcenter 9 is equal to the sum of the rear ends of the plungers 12 but ifdesired the area of the center may be less than the sum of the areas ofthe plungers or vice versa, thereby to augment or decrease the forceapplied to the plungers by the center.

It should be understood that the present disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

I claim:

1. A headstock comprising a rotary head having an axial bore andoff-center bores distributed equidistantly around the center bore, acenter fitted in the axial bore and plungers fitted in the ofi-centerbores, the center and plungers being slidable endwise in said bores,means forcing the plungers outwardly when the center is forced inwardly,and driving dogs having stock-engaging edges, the dogs being pivotallymounted on the projecting ends of the plungers so that said edges areself-aligning.

2. A headstock comprising a rotary head having an axial bore andoff-center bores distributed equidistantly around the center bore, thehead having an interior passageway interconnecting the rear ends of thebores, a center fitted in the axial bore and plungers fitted in theoff-center bores, the center and plungers being slidable endwise in saidbores, said passageway and ends being filled with fluid so that theplungers are forced outwardly when the center is forced inwardly, anddriving dogs having stock-engaging edges, the dogs being pivotallymounted on the projecting ends of the plungers so that said edges areself-aligning.

References Cited in the file of this patent UNITED STATES PATENTS2,191,137 Trible Feb. 20, 1940 2,270,009 Rath Jan. 13, 1942 2,612,071Kurzweil Sept. 30, 1952 FOREIGN PATENTS 100,805 Germany Mar. 17, 1898380,160 Germany Sept. 3, 1923 409,864 Italy Mar. 5, 1945 725,439 GreatBritain Mar. 2, 1955 740,850 Great Britain Nov. 23, 1955 847,672 GermanyJune 26, 1952

